From magnetotransport measurements it is generally believed that Hg-VI compounds show zero gap semiconducting behavior. Applying combined angle-resolved photoemission and inverse photoemission spectroscopy on HgSe(001) $c(2\times 2)$, we observe a positive fundamental gap of about 0.42 eV and a surface related state close to the Fermi level above the conduction band minimum. Following the results of this direct determination of the $\overrightarrow{k}$-resolved band structure, previous experiments favoring zero gap models of Hg-VI compounds need to be reinterpreted.

• Received 13 August 1996

DOI:https://doi.org/10.1103/PhysRevLett.78.3165